Legendary singer Smokey Robinson and actress Gabrielle Union said at the BET Awards, “I think it’s so great that we have a president humble himself, to do something like that.”

Amazing Grace is a song of comfort and inspiration, whether performed by country legend Alan Jackson, a choir of children, or the queen of soul, Aretha Franklin.

So what is it Amazing Grace that makes it so moving? Meghan Linsey sang it on The Voice this past season. "There's so much going on in our country right now, it's a perfect song. People want to hear a message of hope," she told INSIDE EDITION.

But there's a lot you may not know about this iconic song. A 2006 movie, Amazing Grace, tells the story of the man who wrote it -- an Englishman named John Newton. He was a former slave trader who became a priest. He wrote the song about his salvation.

History professor Greg Bandy produced a documentary about Amazing Grace. "This song has been uplifting people for about 250 years, whether it was slaves in a slave camp, or a little country church, the release of Nelson Mandela, the fall of the Berlin Wall, the fall of the Twin Towers, and at Charleston," he said.

Now there's even a new musical about the song that is set to open on Broadway next month.

It’s a moving song -- beloved by many -- that is a comfort to everyone.